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Calculating the Date of Easter
The God Plays Dice blog has an entertaining post on how the date of Easter is calculated. Wikipedia has all the messy details of course, but the blog makes a good introduction to the topic. "Easter is the date of the first Sunday after the first full moon on or after March 21... [T]he cycle of Easter dates repeat themselves every 5,700,000 years. The cycle of epacts (which encode the date of the full moon) in the Julian calendar repeat every nineteen years. There are two corrections made to the epact, each of which depend[s] only on the century; one repeats (modulo 30, which is what matters) every 120 centuries, the other every 375 centuries, so the [p]air of them repeat every 300,000 years. The days of the week are on a 400-year cycle, which doesn't matter because that's a factor of 300,000. So the Easter cycle has length the least common multiple of 19 and 300,000, which is 5,700,000 [years]."
"Easter is termed a moveable feast because it is not fixed in relation to the civil calendar. Easter falls at some point between late March and late April each year (early April to early May in Eastern Christianity), following the cycle of the moon. After several centuries of disagreement, all churches accepted the computation of the Alexandrian Church (now the Coptic Church) that Easter is the first Sunday after the first fourteenth day of the moon (the Paschal Full Moon) that is on or after the ecclesiastical vernal equinox. Easter is linked to the Jewish Passover not only for much of its symbolism but also for its position in the calendar. The Last Supper shared by Jesus and his disciples before his crucifixion is generally thought of as a Passover meal, based on the chronology in the Synoptic Gospels..."
http://en.wikipedia.org/wiki/EasterWikipedia
In the UK school is split into three terms ... in the middle of each, you get a week off, and between them, you get two weeks off. Except over the summer when it's six weeks.
So there's more holiday through the year, but the summer vacation is shorter.
(This is probably because we don't have as much summer.)
Only problem is, your way isn't always right, because the date of Easter is always calculated from March 21st even if (as this year) the northern hemisphere spring equinox doesn't fall on that date.
sub GetEasterDate {
my($year)=@_;
# http://www.smart.net/~mmontes/nature1876.html
my $a=$year%19;
my $b=int($year/100);
my $c=$year%100;
my $d=int($b/4);
my $e=$b%4;
my $f=int(($b+8)/25);
my $g=int(($b-$f+1)/3);
my $h=(19*$a+$b-$d-$g+15)%30;
my $i=int($c/4);
my $k=$c%4;
my $l=(32+2*$e+2*$i-$h-$k)%7;
my $m=int(($a+11*$h+22*$l)/451);
my $month=int(($h+$l-7*$m+114)/31);
my $p=($h+$l-7*$m+114)%31;
my $day=$p+1;
return (0,0,0,$day,$month-1,$year-1900);
};
$x='S24;r)>63/* h@<5+oZ)32"5cz';$me='phroggy'x$];
$x=~y+ -xz+\0-Tx+;print$_^chop$me for split'',$x;
Absolutely - the Anglo-Saxons had a lot to say about the dating of Easter. See http://faculty.virginia.edu/OldEnglish/aelfric/detemp.html for an original text on the subject if you're wildly interested. Melvyn Bragg's novel "Credo" dramatises the Synod of Whitby and gives a sense of exactly how serious an issue this was for people. Since Easter is the major Christian feast, it was a matter of orthodoxy to date it correctly. Interesting to think that being bad at math could make you a heretic!
A closed mouth gathers no foot.
the way he would have had to if this were a Muslim story
Or, you know, a Jewish or Christian one. The penalty of death by stoning for adultery is straight out of the Old Testament.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
Even worse... there are Christian women on /.
Seriously, do you assume that all Christians are no-brain idiots who think dinosaur skeletons are an atheist conspiracy? Donald Knuth is a Lutheran, Gregor Mendel was an Augustinian monk, Copernicus was a priest, as was Georges Lemaitre. Lord Kelvin and Max Planck were committed Christians, Arthur Stanley Eddington was a Quaker... There are more here: http://en.wikipedia.org/wiki/List_of_Christian_thinkers_in_science (Not all of those in this list were Christians throughout their lives, but the ones I've named were/are.)
A closed mouth gathers no foot.
The date IS fixed -- it's all a matter of perspective. Dates are divisions of a calendar, and a calendar tracks time using periodic and regular astronomical events. Obviously, the easiest of these is the day, since it's easy to tell when the sun rises, and our body clocks (and therefore the work day) are tuned to it. Unfortunately, days are too granular: to really organize a civilization, you need larger logical units (such as weeks, months and years). Nowadays, we use a calendar which tracks the sidereal year -- the time it takes for the earth to complete one full orbit. For agricultural purposes, this is ideal, since it will tell you when to grow your crops. Unfortunately, it was a tricky one to calculate: even if you know that the earth orbits the sun, you're stuck dealing with the fact that the orbit is nearly circular so you can't find a visible difference in size in the sun, and the stars are so incredibly distant that there's no appreciable parallax. One cue that you CAN watch for is the equinox, and this is exactly what early calendars did to track the seasons. Your typical farmer isn't going to have the time or the tools to measure when the day and night are of equal length, but he can get a general feel for it, and you can have a few people set aside whose job in the springtime is to watch the length of each day.
For the common man, an easier thing to watch is the moon. The phases of the moon are not only regular, but they're highly visible and uncomplicated. This means that if your calendar has something to do with the moon, then it's not only easy for your astronomers to track, but it's easy to explain to the unwashed masses: just tell them the festival is on the next new or full moon, and they'll know exactly what you mean. You can also track days for a very small number of days; 7, for instance. You can tell people "go out and work really hard for 6 days, and on the seventh, take a break," and most people can do that (and those that can't can just notice that those who can aren't working on some days). In the Jewish tradition, as you're probably aware, the seventh day is called the Sabbath, and is considered sacred.
A mix of the two was popular -- the accessibility of the lunar calendar was nice, but the agricultural significance of a sidereal calendar was needed as well. For the Liturgical year, the calendar starts with the first new moon after the spring equinox. This means that there's not even any pretense that the calendar is equivalent to a sidereal year; the orbital period of the moon just isn't any fraction of the orbital period of the earth.
Easter tries to mix the 3 logical units of measurement: the rules are complicated, but it essentially boils down to finding a date which 1) falls on a Sabbath, 2) comes quickly after an equinox and 3) ties into lunar phase. The way they chose was to set it at the first Sabbath following the first full moon following the spring equinox. But, approximations are applied to make it easier to plan: ancient astronomy was amazing for what they had at their disposal, but really very far from perfect. So, since the need to plan out a major annual festival was superior to the need for people to be able to look in the sky and see it get close, approximations were accepted over time. The "full moon" was assumed to occur 14 days after the new moon, which was in turn predicted from tables generated using an agreed-upon system of reckoning. The equinox was eventually taken to occur on March 21. The end result is that it no longer actually directly corresponds to an equinox or a lunar phase, and is instead based off of approximations that were chosen to make the date easier to work with. Nowadays, the approximation that most proponents of Easter date reform put forth is just to pick something like the first Sunday of April and use that. Others want to go back to a pure lunisolar basis and throw out the approximations. At this point, however, there's not much motivation to do either: we can compute Easter out arbitrarily far now, and it's printed on every c
Yes and no. In the Hebrew Bible, the word used by Isaiah is rightly translated as "young woman." In the Septuagint (the Greek translation of the Hebrew Bible produced nearly 200 years before Christ, and much older than the oldest extant Hebrew language Bible), however, the word is in fact "virgin."
Many Christians themselves, not to mention those who don't know much about the religion (no offense, but the majority of /.), are unaware of the fact that the Apostles themselves would most likely have used the Greek scriptures--indeed, it is apparent throughout the New Testament that the Hebrew scriptures being quoted nearly all are of Septuagintal origin.
To reign is to serve.